#! perl
my @should_match =
(
    '123-456-789',
    '123.789.456',
    '963 456 741',
);

my @should_not_match =
(
    '123-456.789',
    '123 789-456',
    '963.456 741',
);

my $re = qr/\d{3}([ .-])\d{3}\1\d{3}/;

for (@should_match)
{
    if ($_ =~ $re)
    {
        print "ok\n";
    }
    else
    {
        print "failed\n";
    }
}

for (@should_not_match)
{
    if ($_ =~ $re)
    {
        print "failed\n";
    }
    else
    {
        print "ok\n";
    }
}